/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    string tree2str(TreeNode* root) {
        
        string s;
        if(root==nullptr)
        {
            return "";
        }


        s+=to_string(root->val);

        if((root->right!=nullptr&&root->left==nullptr)||(root->left!=nullptr&&root->right!=nullptr))
        {
            s+="(";
            s+=tree2str(root->left);
            s+=")";

            s+="(";
            s+=tree2str(root->right);
            s+=")";
        }
        else if(root->left!=nullptr&&root->right==nullptr)
        {
            s+="(";
            s+=tree2str(root->left);
            s+=")";
        }
        
        return s;
    }
};